Case Study #3 - Silo Safety
AKO Pinch Valves Protect Silos from Damage

Silo over pressurization has resulted in a number of potentially serious incidents. For example filter housings weighing hundreds of pounds and powder products have been ejected from the tops of silos. At least one serious injury has occurred because of this problem. As well as the more obvious dangers there is a potentially huge risk to the environment if an explosion should occur.

Potentially all companies with storage silos need to be aware of the problem and take steps to ensure the safe filling of them.

When pumping powder, particle or granular products into a silo, increasing air pressure can sometimes cause damage to the silo and more seriously bystanders can be injured if an explosion occurs. At the very least silos can be overfilled, causing waste and/or contamination of product, costing costly losses.

AKO have launched a unique system for rapid and safe filling of silos, using a pinch valve and special solenoid valve to control the product flow. ‘Standard’ pinch valves are known to fail open, but this system overcomes the problem while maintaining all the benefits of using a pinch valve in this application instead of a butterfly valve.

Previously standard pinch valves have failed open, but using a unique RGS solenoid valve on the system the pinch valve will fail closed. If the system has lost air and the pinch valve is in the closed position it will remain closed until an engineer can resolve the problem. When the pinch valve is open and the driver is unloading his truck into the silo, loss of air is detected by a pressure switch and again the pinch valve immediately closes.

The AKO pinch valve is permanently mounted in the silo input line. As the tanker discharges its product load using its own integral compressor, a paddle switch mounted in the top of the silo senses the increasing level of silo content. When the movement of the rotating paddle is restricted by the rising level, rotation ceases and a microswitch is tripped, sending a signal to the solenoid on the pinch valve. The solenoid activates instantly and allows air pressure to close the sleeve in the pinch valve. Simultaneously the pinch valve triggers an audible alarm advising the truck driver to stop his compressor.

Controlled filling systems using butterfly valves are occasionally used on silo safety systems, but the flow through the valve is restricted by the butterfly disk, slowing down the filling process. The valve seat becomes contaminated with trapped product, resulting in spillage, waste and crosscontamination. The butterfly disk also wears very quickly increasing maintenance costs and down time.

The use of a pinch valve eliminates these problems immediately. A full bore 4 inch diameter valve allows unrestricted product flow. Tanker discharge time can be effectively reduced by more than 10%. FDA approved white rubber sleeves can be supplied with stainless steel contact parts for handling foodstuffs and pharmaceuticals.

Pinch valves have been used for many years in many abrasive applications. Due to the sleeve technology clear bore and simplicity of the pinch valve, the life in certain applications can be up to 6 times longer than a butterfly valve.

Simple maintenance with the AKO Pinch Valve not only puts it way ahead of ‘traditional’ valves, but also other pinch valves on the market. AKO Pinch Valve sleeve replacement can be completed in approximately 5-15 minutes depending on the size of the valve. Replacing only the sleeve means a fraction of the maintenance cost compared with repairing a butterfly valve.

For more information on AKO pinch valves and accessories please call +614.873.8995